1. Field of the Invention
The invention relates to a support system in which an object can be supported free from vibration such that it can behave as if it floats freely, uncoupled from its environment. That object may be a platform or worktop or table, on which an experimenting arrangement can be built up, and the invention will therefore hereinafter be described for such a practical example. However, it will be understood that other practical examples are also possible, for instance specific parts in a positioning system.
2. Description of the Related Art
An important requirement imposed on such a platform is that the platform is positioned free from vibration, i.e. environmental vibrations must not be felt in the platform and the experimenting arrangement built thereon. This entails the problem that the platform must somehow be supported relative to a fixed world (floor), for instance for counteracting gravity, which fixed world is generally not free from vibrations.
An important requirement imposed on such a platform is that the platform is positioned free from vibration, i.e. environmental vibrations must not be felt in the platform and the experimenting arrangement built thereon. This entails the problem that the platform must somehow be supported relative to a fixed world (floor), for instance for counteracting gravity, which fixed world is generally not free from vibrations.
Generally, the bearing or suspension of the platform can be regarded as a spring system. Vibrations in the outside world cause length variations in the spring system, which length variations are translated into variations in the force F exerted on the platform by the spring system. That force F can generally be described by the known formula       F    =                  m        ⁢                                            ⅆ              2                        ⁢            x                                ⅆ                          t              2                                          +              c        ⁢                              ⅆ            x                                ⅆ            t                              +      kx        ,
where x represents said length and k represents the stiffness of the spring system. For vibrationless support systems, it is desired that k be as small as possible.
Conventionally, damping elements having a low stiffness are incorporated into the support or suspension, for instance rubber blocks in the support or long, weak springs in the suspension, and the platform is constructed with or attached to a heavy mass. Because of the low stiffness of the damping elements, force variations are relatively low, and because of the heavy mass of the platform, the vibration amplitudes caused by the force variations are relatively small. However, this conventional approach yields insufficient result.
A better result is provided by a support system in which the support for the platform has a working point in which the stiffness is zero, while within a certain working area around that working point, the stiffness has particularly low values. However, known support systems with zero stiffness have a number of drawbacks, as will be discussed in more detail hereinbelow.
It is a general object of the present invention to eliminate the drawbacks of the prior art.
More in particular, it is an object of the present invention to provide a zero stiffness support system wherein there is no mechanical contact between the platform and the fixed world, wherein, in principle, no external energy is required for supporting, and wherein the system has a particularly simple and compact construction.
In accordance with an important aspect of the present invention, the positioning system comprises at least two electric or magnetic couplings, one of which exerts a repulsive force of a positive stiffness on the platform, and the other one of which exerts an attractive force of a negative stiffness on the platform, in such a manner that the sum of said forces has a zero stiffness in a working point.
These and other aspects, features and advantages of the present invention will be clarified by the following description of a preferred embodiment of a support system according to the invention, with reference to the accompanying drawings, in which identical reference numerals denote identical, or comparable parts, and in which: